I just bought yesterday a Hydra 16 Catamaran to perform my experiments.
I would like to convert it to solar powered vessel for family flat water cruising.

My experiment will be to establish what will be maximum speed when powered by:

a) electric outboard motor 1,152 Watts 86 Lbs 24 V - that I purchased already

b) Suzuki outboard 4 stroke 6 HP -planing to buy one this week

I assume that catamaran will be carrying two people weight - 150 kg, and all rigging removed (mast) just hulls.
I am not sure if I still need rudders or could just use motor to steer the boat.

I wonder is somebody want to guess or know already what max speed will be achievable in a) and b).
I should know all results in week or two.





Next question if catamaran hulls powered by 6HP motor will be faster and more efficient then small dingy ( some may say that small boats could get planning with as small motor as 3 HP ?? )

My guess is, for the 1152 watt electric motor you will get about 2 or 3 knots out of it.
For the 6hp petrol motor (about 4500 watts) you will get about 6 to 8 knots.

Be aware that for the electric motor to run at the full 1152 watts for just one hour on 24 volt battery, you will need a battery with at least a 50 amp hour capacity,. when it's new. This will progressively de-rate with age.

As for solar panels, you will need 6 x 200 watt panels to produce the same power provided that it is in the middle of the day and the sun is shining and nobodys shadow is over any of the panels.

In practical terms, I think you will be able to use just one or two panels to charge up the battery and the main power will have to be provided by the battery. I don't think you have room on a smal cat for that.

All up, as far as energy density goes, the petrol outboard is far and away the best prospect, but they are noisy little effers.

Electric motors are only good for fishing where you are just slowly trolling along at maybe less than one knot and using about 200 watts. For this they are ok. Nice and quiet and you get about an hour out of a small 10 amp hour battery. (24 volt)

I find it hard to imagine that a boat of any size could plane with a 3hp motor. (about 1500 watts)
I think we worked it out a while back that it takes about 5hp and more to get a windsurfer planing.

Post up the results when you get it all going. I'm interested to see how it goes.

I would highly not recommend buying a 4 stroke 6 hp.... The best outboard is the tohatsu 5 hp single cylinder. The four strokes are much heavier,louder and expensive.

Remember, Cats don't plane, they cut.
So perhaps the references to planing aren't overly relevant.

Macro, good luck. Obviously you won't want to venture too far with Solar/Electric only. I can already 'smell' a potential stranding... no power left...!

1.At this moment I have plenty of LiFePO4 batterries in 24 36 and 48 V in 10 and 20 AH that I could use for my test. Leftover form my EV experiments .But all batteries will eventually get dry faster that I could expect - that from my electric bike that never did expected range.
That is why I want to use solar panel to recharge in the same time.

2. Solar panels. There is a problem. As standard panels are already reasonable cheap, but heavy and may not withstand constant salt water splashing.
I think about 1 to max 2 kw solar.
My total available area is limited by boat dimensions: that is 5.0 meters long and 2.4 m wide. But my friend that has also Hydra 16 extended that width actually to 4.0 m.
Since I need to tow on the trailer - maybe some sort of collapsible extenders ??

Because of the weight of traditional solar panels I may need to use flexible panels but at this moment there are 5 x more expensive

3. As a booster and backup I want to use for electric version petrol generator 1-2 kw. But because of the safety I don't want to use standard generator 240 V then convert down to 24 V. I want to use all DC 24V generator only and although not available at this moment anywhere I managed to find manufacturer and would try to import directly. Should arrive in next 3 month.

4. Petrol outboard. For test I want to use simple outboard as is easy available, reasonable cheap and should be reliable. I have been considering 2 stroke first, but for two reasons I decided for 4 stroke
- easier to start up - at least with my power tools experience so far
- cleaner fumes
- I thinks that 6 HP is actually max I could use without the need for registration to I think Suzuki 6 HP or Honda 5 HP (?) I need to decide quick and buy one this week.

I get 17knts with my 5 tohatsu and new RIB inflate able with the ally v bottom.

theDoctor said...


crazy idea, why not put a mast and sail on the catamaran....?

Well, I have been sailing cat for years. Hobbie 16 .
Time to try something new...I never had powered boat...

advantage for such powered boat is easy to navigate our complex Gold Coast channels..
the interesting question will be the speed - which could indicate the range of daily family trip.
I will be extremaly happy if I could reach Brisbane and go back - approx 200 km in one day on my finished boat.
I wonder is 200km range is realistic for electric powered DIY cat.

BTW I love my Hobbie too much to violate it and convert into powered boat
so I did purchased Hydra...

Look Makro, here are some calculations, and I'm afraid you won't like them

For your 2 kW solar system, you'll need an area of about 10 m2 (assuming 1 kW solar power per m2 at noon and 20% panel efficiency).

However, that's the system's peak output. Average insolation levels in Qld will give you 4.2 kWh of daily energy per 1 kW of system output :
http://forums.whirlpool.net.au/archive/1549668

That's for an arangement which is not heliostatic, but not horizontal either (i.e. the panels are fixed at a reasonable northern aspect and don't track the sun). For your boat, the most feasible arrangement may be fixed flat horizontal panels, but let's assume you manage to implement a rudimentary tilting mechanism, and achieve the same capacity levels as a fixed rooftop installation...

So, you'll get 8.4 kWh of energy out of a 2 kW system on an average day.

The energy contained in 1 litre of petrol is the equivalent of 9 kWh: en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equivalent

So, with your 2 kW solar system over 1 day, you will be lucky to get as far as with 1 litre of petrol. Actually you may just get about as far, due to some efficiency advantages of the electric route, but certainly not much further...

You'll need plenty of batteries...

d1 said...

You'll need plenty of batteries...

My standard electric bike LiFePO4 battery 24 V 10 Ah = 240 Watt/hours
which mean that standard electric bike battery last for only 15 minutes electric outboard
My biggest LiFePO4 batteries are 48V 20 Ah -which in perfect conditions should supply power for 1 hour. I have three so it should be enough for 3 extra hours, just have to find a DC to DC converter 48 to 24V

I reckon you'll make Fiji and back no probs, give it a crack.

Put 15 horses on it and forget economy. You want to get somewhere don't you??

When you get sick of that farce, buy a 3.5 m tinnie or inflatable and put the 15 horses on the back of it.

One boat for sailing, another for motoring and ne'er the twain shall meet.

Why do you try to make something into something else that it can never be?

southace said...
I get 17knts with my 5 tohatsu and new RIB inflate able with the ally v bottom.

Landyacht how old is your tohatsu mine is 6 months old and purs like a kitty. I can hear them 4 strokes a mile always sounding like someone mowing the lawns.

Macroscien said...

theDoctor said...


crazy idea, why not put a mast and sail on the catamaran....?

Well, I have been sailing cat for years. Hobbie 16 .
Time to try something new...I never had powered boat...

advantage for such powered boat is easy to navigate our complex Gold Coast channels..
the interesting question will be the speed - which could indicate the range of daily family trip.
I will be extremaly happy if I could reach Brisbane and go back - approx 200 km in one day on my finished boat.
I wonder is 200km range is realistic for electric powered DIY cat.

BTW I love my Hobbie too much to violate it and convert into powered boat
so I did purchased Hydra...

Why not try a kite?

evlPanda said...

Macroscien said...
Next question if catamaran hulls powered by 6HP motor will be faster and more efficient then small dingy ( some may say that small boats could get planning with as small motor as 3 HP ?? )

Er, definitely not.

unless its one of these hulls





its a catamaran, its light weight, it has a reliable lightweight tohatsu, its economical ( not at full throttle though )

approx 13ft
more stable than a tinnie ( two adults can stand on one hull and the other wont leave the water )
lighter than a tinnie at 90kg
faster than a tinnie ( over 100kmh / 55knots ) if you want.
lightweight reliable proven 2 stroke Tohatsu motor.
draws less than 10cm at full noise
will plane at approx 10-15knots


second hand for less than $5000 ( may require some minor work )

more fun than you can poke a stick at

Macroscien said...

kiteboy dave said...
There's a whole lot of reasons a 10ft tinnie + 6hp (or 12/8 etc) is such a common small boat combo. Cheap, reliable, does everything well. Your cat is designed to be a sailboat and won't be wonderful as runabout - too heavy, doesn't turn well, etc

Also I know english isn't your first language so just for your info some might be confused by you using 'planing' and 'planning' backwards. Planing is what a boat does.

This will be very interesting to find out what is the most efficient at lower motor power.
Small tinnie that could plane with 6 Hp engine or small cat with 1.1 Kw electric motor.
I am sort of green geek and that will be interesting to find out which one needs less energy to travel over 100 km distance.

The sail!
The sail will use less energy to travel. Also, it won't weigh half a tonne and doesn't mind a bit of salt water; batteries on the other hand....

harry potter said...

evlPanda said...

Macroscien said...
Next question if catamaran hulls powered by 6HP motor will be faster and more efficient then small dingy ( some may say that small boats could get planning with as small motor as 3 HP ?? )

Er, definitely not.

unless its one of these hulls





its a catamaran, its light weight, it has a reliable lightweight tohatsu, its economical ( not at full throttle though )

approx 13ft
more stable than a tinnie ( two adults can stand on one hull and the other wont leave the water )
lighter than a tinnie at 90kg
faster than a tinnie ( over 100kmh / 55knots ) if you want.
lightweight reliable proven 2 stroke Tohatsu motor.
draws less than 10cm at full noise
will plane at approx 10-15knots


second hand for less than $5000 ( may require some minor work )

more fun than you can poke a stick at

Engine cooling not a problem? Can see gearbox housing on outboard and the water intake is normally located above this. Obviously seaworthiness and safety don't figure either due to the sun protection the guy is wearing.